1. Field
The present invention relates to devices designed to secure a ladder to a tree or pole to prevent movement of the ladder while an operator is on the ladder.
2. Prior Art
There have been a number of prior art approaches to provide a safe method of securing a ladder to a tree, however, most have proven unwieldy or actually unsafe during the initial attachment phase. For example U.S. Pat. No. 4,469,195 shows a caliper gripping mechanism that uses a pulley and line system to open the calipers to enable them to fit about a tree. A spring's tension is the only force used to drive the calipers into the tree. The spring is stretched widely about relatively large diameter trees and after repeated stretching may lose some of its resiliency, especially when it is used with trees or poles having a relatively small diameter. This problem is made worse by the fact that even initially with a new spring, the tension force produced by the spring varies with the amount it is stretched and tension is relatively less when it is stretched only a relatively short distance, as would be the case with small diameter trees or posts.
In U.S. Pat. No. 4,363,378 the ladders top most rung is curved to accommodate the curvature of a tree or pole. The operator must climb to the top to secures a metal band about the pole. The difficulty encountered with this approach is the curved rung does not prevent the ladder from rotating or sliding about the pole while the operator is in the initial climb to secure the ladder with the metal band.
In U.S. Pat. No. 4,946,004 pivotally mounted caliper gripping arms are forced to enclose a tree by resting the ladder against the tree. There is no locking mechanism which secures the arms about the tree. Wind or a misplacement of weight by the operator can cause the arms to release, resulting in no securing action by this device when it may be most needed. These problems and others are overcome in the present invention, as described below.